If in Ubuntu Grub2 is not detecting Windows 7 or Fedora or some other OS, try this.
1) gksudo gedit /etc/default/grub
2) Look for a line that reads : GRUB_DISABLE_OS_PROBER=”true”
3) Comment out that line by placing a # at the front of it.
Like so:
#GRUB_DISABLE_OS_PROBER=”true”
Save the file.
4) Run sudo update-grub2.
5) Check the results.
6) Reboot.
Your menu with all Operating systems should now be available.